This application is based on Application No. 2001-172703, filed in Japan on Jun. 7, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a control unit for an internal combustion engine, and in particular to the detection of abnormality in an internal combustion engine and the generation of warnings based on the abnormality detected.
2. Description of the Related Art
FIG. 4 is a schematic constructional view illustrating those portions of such a kind of known control unit for an internal combustion engine which relate particularly to the detection of abnormality and the generation of warnings based on the abnormality detected. In this figure, the control unit for an internal combustion engine (hereinafter abbreviated as ECU), generally designated at a reference numeral 1, is connected with abnormality detection devices 2 (though only one is illustrated) such as a variety of kinds of sensors, switches and so on, for example, for controlling the internal combustion engine (hereinafter simply referred to as an engine), and with warning devices such as a lamp 3 and a buzzer 4 for informing a user (driver, passengers, etc.) of the occurrence of abnormality based on the detection thereof.
The ECU 1 includes a control CPU 5, input interface (xe2x80x9cI/Fxe2x80x9d) circuits 6 provided one for each of the abnormality detection devices 2, output I/F circuits 7a, 7b provided one for each of the warning devices comprising the lamp 3, the buzzer 4, etc, an input side connector 1a having a plurality of input terminals 2p provided one for each of the abnormality detection devices 2, and an output side connector 1b having a plurality of output terminals 3p, 4p provided one for each of the warning devices 3, 4.
FIG. 5 particularly illustrates the circuit structure of one input I/F circuit 6 and one set of output I/F circuits 7a, 7b of the known control unit for an internal combustion engine of FIG. 4. The input I/F circuit 6 includes a transistor Tr1, pull-up resistors R1, R2, a diode D1 for protection from an external negative surge voltage, and a combination of a capacitor C1 and a resistor R3 together constituting an RC filter for preventing chattering by smoothing an input signal to the transistor Tr1.
The output I/F circuits 7a and 7b include transistors Tr1a, Tr1b, pull-up resistors R11a, R11b, resistors R12a, R12b connected with the base sides of the transistors Tr11a, Tr11b, respectively, and resistors R13a, R13b connected with the collector sides of the transistors Tr11a, Tr11b, respectively.
Now, the operation of the circuit of FIG. 5 will be described briefly. When abnormality is detected by an abnormality detection device 2, this abnormality detection device 2 shown as a switch in FIG. 5 is closed, whereby the transistor Tr1 of the input I/F circuit 6 is placed into an off state, permitting a high (H) level signal representative of the detection of abnormality to be input to the CPU 5. As a result, the CPU 5 outputs H level signals to the output I/F circuits 7a, 7b, respectively. That is, current is supplied from a power supply Vcc to the transistors Tr11a, Tr11b, which are thereby turned on, driving the respective warning devices such as the lamp 3 and the buzzer 4 to generate warnings of light and sound.
In the past, the control unit for an internal combustion engine, i.e., ECU 1, performs various control operations (e.g., ignition timing control, fuel injection control, etc.) for the internal combustion engine, and at the same time detects various abnormality states of the engine thereby to generate warnings to the user (in general, the driver).
To this end, there are provided the abnormality detection devices 2 such as, for example, various sensors, switches and the like, and the warning devices such as the warning lamps 3, the warning buzzers 4 and the like. Connected with the ECU 1 are abnormality detection devices 2 and the warning devices 3, 4 for detecting and warning of the above-mentioned abnormal states, so that the detection of abnormal states and the generation of warnings are controlled by means of the CPU 5 incorporated in the ECU 1.
Here, it is to be noted that the input I/F circuits 6 and the input terminals 2p equal in number to the abnormality detection devices 2 are required though only one for each of them is illustrated in FIGS. 4 and 5 for the sake of concise explanation. Also, the output I/F circuits 7a, 7b and the output terminals 3p, 4p equal in number to the corresponding warning devices 3, 4, are required though only two of them are illustrated in FIGS. 4 and 5 for the sake of concise explanation.
In this manner, one or more warning devices is generally provided for one abnormality detection device in this kind of known control unit for an internal combustion engine, and hence two or more input terminals and output terminals of the control unit for an internal combustion engine are necessary.
At present, the number of kinds of warning control operations to be performed in the control unit for an internal combustion engine, i.e., the ECU, tends to increase, and hence the number of input and output terminals accordingly increases, too. As the number of the input and output terminals increases, the number of terminals of the connectors to be used accordingly increases, too. In addition, the size of the connectors also increases, thus resulting in an increase in size of the ECU.
In these circumstances, connector manufactures are now in the process of developing connectors with many terminals in order to cope with the increasing number of the input and output terminals. However, there is a tendency that the connectors newly developed in this manner become greater in size than the existing ones.
On the other hand, the configuration of the engine surroundings are also becoming more and more complicated in accordance with the increasing power, environmental response, etc., of an engine. As a consequence, miniaturization and weight reduction of the ECU come to be important problems.
The present invention is intended to obviate the problems as referred to above and has for its object to provide a control unit for an internal combustion engine in which the number of input and output terminals can be reduced for miniaturization and weight reduction thereof while maintaining the function of detecting an abnormality of an existing internal combustion engine and generating a warning based thereon.
Bearing the above object in mind, the present invention resides in a control unit for an internal combustion engine comprising: an input and output I/F circuit connected through a common signal line with an abnormality detection device, which generates an abnormality detection signal when an abnormality of the internal combustion engine is detected, and with at least one warning device, which generates a warning based on the abnormality detected, the input and output I/F circuit being adapted to receive an abnormality detection signal from the abnormality detection device and output a drive and hold signal to the warning device; and an arithmetic processing section for controlling the abnormality detection device and the warning device through the input and output I/F circuit in such a manner that a drive and hold signal is output to the warning device when the abnormality detection signal is input to the arithmetic processing section.
In a preferred form of the present invention, the control unit is provided with one input and output terminal for the one common signal line.
In another preferred form of the present invention, the arithmetic processing section disregards an abnormality detection signal from the abnormality detection device during the period in which a drive and hold signal is output to the warning device.
In a further preferred form of the present invention, the arithmetic processing section generates a drive and hold signal to the warning device for a predetermined period while disregarding the abnormality detection signal for the predetermined period when the abnormality detection signal is detected through the input and output I/F circuit, and the arithmetic processing section begins to detect the abnormality detection signal again after the lapse of the predetermined period.
In the present invention, an abnormality detection devices and warning devices responding to the abnormality detection device are commonly connected in parallel with one input and output terminal of a control unit for an internal combustion engine. The input and output terminal has an I/F circuit which is constituted by an input and output I/F circuit in which an input I/F circuit having the function of detecting an input from the abnormality detection device and an output I/F circuit having the function of driving and holding the warning devices are arranged in parallel with respect to each other. These input I/F circuit and output I/F circuit are connected with an input terminal and an output terminal of a CPU, which acts as an arithmetic processing section, so that the CPU carries out control on warning generation.
As a result, it can be constructed such that the control unit for an internal combustion engine uses a reduced number of input and output terminals while having the same warning generation function as an existing one. Thus, it becomes possible to reduce the number of terminals (e.g., the number of pins) of connectors to be used and at the same time achieve reduction in size and weight of the control unit for an internal combustion engine.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of a preferred embodiment of the present invention taken in conjunction with the accompanying drawings.